Design of a Switched-Capacitor DC-DC Converter with a Multiple Up/Down Ratio

The characteristics of electric energy obtained from the energy harvesting devices is unstable unlike that obtained from a battery or a traditional external power source. This work proposes a DC-DC converter design based on switched-capacitor voltage converter, which constrain unstable output from energy harvester to a certain level. The converter provides ten conversion ratio includes 1/4, 1/3, 1/2, 2/3, 3/4, 4/3, 3/2, 2/1, 3/1, and 4/1 to achieve this operation. The implemented hardware consists of 16 commercial analog switches and four 1uF capacitors. FPGA based controller also implemented for generating PWM signals to control switches. The averaged conversion efficiency is 79% through all conversion ratio for a fixed input voltage of 1V and a fixed output current of 1 m.A.